Fluid operated motor



Sept. 17, 1957 J. R. SIMMONS FLUID OPERA'IIED MOTOR 2 Sheets-Sheet 1 Filed March 3, 1955 Sept. 17, 1957 J. lan-SIMMONS FLUID OPERATED MOTOR Filed March 5, 1955 2 Sheets-Sheet 2 FLUID OPERATED MOTOR John Roy Simmons, Cordele, Ga., assignor to Harris Foundry & Machine Co., Cordele, Ga., a corporation of Georgia Application March 3, 1955, Serial No. 491,989

11 Claims. (Cl. 121-38) The present invention relates to fluid apparatus, and, more particularly, to a reciprocating fluid motor which may directly actuate, or serve `as a servo-motor for actuating, any `of an infinite variety of mechanisms.

More especially, this invention relates to a three-position lluid motor that can be controlled by a simple fourway valve.

It is a primary object of this invention to provide an improved three-position fluid motor. Y

It is another object of this invention to provide a fluid pressure motor which may be easily constructed-from readily 'available materials with ordinary tools and which represents an advancement in design inasmuch as the number and complexity of Working parts are reduced.

It is another object of this invention to provide a fluid pressure motor which may be economically constructed and which, due to its simplicity, may be operated for long periods of time with 'a minimum of maintenance.

It is another object of this invention to provide a iluid pressure motor which may be easily and rapidly assembled and installed and which may be quickly broken down for any necessary inspection, maintenance and repairs.

It is a further object of this invention to provide an improved fluid pressure motor which can be used in combination with standard and easily obtainable control -apparatus of standard makes, shapes, sizes and capacities.

These and other objects of the invention willbe fully understood from the following detailed description of a typical preferred form and application of this invention, throughout which description reference is made to the accompanying drawings i'n which:

Figure l is a longitudinal section of a fluid pressure motor embodying this invention and showing the motor in its intermediate position.

Figure 2 is a View corresponding to Figure l but showing the motor `in one of its two extreme positions.

Figure 3 is a view corresponding to Figure l, but showing the motor in the other extreme position. p

Figure 4 is a schematic showing of a hydraulic control circuit for operating the motor shown in Figure l.

Referring to Figure l, a fluid pressure motor 10 ernbodying this invention comprises an elongated hollow cylinder 12, having the forward end thereof closed, as by a plug 14, :and having the rear end thereof closed, as

by plug 16. Preferably, the plugs 14 and 16 seat againstcorresponding interior shoulders 18 formed by counterbores in the ends of the cylinder and are retained in place by split snap rings 20 and 22, respectively. The plugs 14 and 16 are sealed to the cylinder by O-rings 24 and 26, respectively, disposed in circumferential grooves in the plugs and engaging the interior counterb'ored surfaces of the cylinder.l The cylinder, between the plugs 14 and 16, has 'a smooth-walled bore 27 of uniform diameter and has a side wall port 28 adjacent one end of the bore just inwardly of the plug 14 and has a side wall port 30 located at or near the mid-point `of the length of the bore 27. The end plug 16 has its inner face recessed, las at 32, to receive the stub end 34 of a piston rod 36, and has atent ice a longitudinally extending port 38 formed therein. Ports 28, 30 and 38 may be suitably tapped to receive a threaded end of a pressure-fluid conduit, as will be discussed hereinafter.

It should be here stated that while port 38 is illustrated as being in the end plug 16 and port 28 is indicated as being in the side wall of the bore 27, it is entirely within the contemplation of this invention that the relative position of these ports may be reversed, or that both ports may be in either the end plugs or in the bore side wall.

Slidably disposed within the cylinder 12 is a pair of tandemly 'aligned tubular pistons 40 and 42, which preferably are identical for convenience of manufacture and interchangeability. The inner, or neighboring, ends vof the tubular pistons have inwardly extending abutment means which preferably consist of circumferential anges 44 and 46, respectively. The tubular pistons 40 and 42 are also provided with exterior peripheral collars 47 and 48, respectively, which are longitudinally located somewhat inwardly of the outer ends of their respective pistons. Thus the collar 47 is located somewhat inwardly of the port 28 so that pressure-fluid admitted therethrough will act on the outer ends of the piston 40 when the latter abuts the end plug 14, as shown in Figures 1 and 2. The collars 47 and 48 may be suitably iixed to the tubular pistons 40 and 42, respectively, or may be cast, or otherwise formed, integral therewith. The peripheral surfaces of the collars 47 and 48 are provided with circumferential grooves having O-ring seals 50 and 52, respectively, therein which serve as piston rings to seal with `the cylinder bore 27.

When the fluid motor is in its intermediate positionX as shown in Figure l, the tubular pistons 40 and 42 abut the end plugs 14 and 16, respectively, Iand have their neighboring ends, which are provided with flanges 44 and 46, respectively, spaced apart a substantial distance.

An imperforate piston 54, having a piston rod 36 iixed thereto or formed integrally therewith, is disposed coaXially within the tubular pistons 40 and 42. The piston rod 36 extends outside the cylinder 12, for connection to any mechanism to be operated, through a central aperture S6 in the forward end plug 14. To effect a seal between the rod 36 and the aperture 56, the inner periphery of the aperture is provided with a circumferential groove having `an O-ring seal 58 therein. As illustrated in Figure l, the piston 54 extends between, and within, the two tubular pistons 40 and 42, when the latter are in their spaced positions shown in Figure l. The piston 54 is formed as :a smooth cylinder dimensioned to slide within the franges 44 and 46, and has its ends provided with abutments 60 and 62 extending radially therefrom a sufficient distance to engage the llanges. In the preferred illustrated embodiments, at least one of the abutments is detachable for assembly purposes. Hence, the abutment 60 may consist of a collar formed integral with the piston, while the abutment 62 consists of a washer mounted on a stub end of the piston rod 36 and fixed thereto, as by a snap ring 64, in an abutting relationship to the piston.

The inner periphery of the flanges 44 and 46 are provided with 'circumferential grooves having O-rings 66 and 68, respectively, therein which sealingly engage the piston 54.

It will be seen that the seals 50 and 52, together with seals 66 and `68, serve to segregate the interior of the cylinder 12 into 'three chambers 70, 72 and 76, here termed the forward pressure chamber, the intermediate 76 will vary during the operation of the motor, although the Sum total of their volumes remains constant, except as affected by the volumetric displacement of the piston rod 36.

The seals alone define the pressure chambers, and all sliding or -contacting metal surfaces, not provided with seals, allow the pressurized duid to pass freely therebetween. For example, while the tubular piston 40 has been illustrated (Figures 1 and 2) Vas abutting the forward end plug 14, it should be clear that no pressure seal is affected lbetween these two members, and it is within the contemplation of this invention that the outer end faces of the tubular pistons 40 and 42 may he radially grooved or otherwise formed, if necessary, to allow a yfree flow of pressurized fluid around their ends.

Referring more particularlyv to Figure 4, in which there is illustrated av schematic diagram of the uid pressure motor operatively connected into a hydraulic circuit including a simple control valve 78 for operating the motor, it ywill be seen that the motor has its intermediate port 30 constantly in direct fluid communication, via conduits 30 and 82, with a source of pressure-fluid, here shown as the discharge side of a pump '84, which withdraws fluid from a sump yor reservoir 86. The discharge side of the pump 84is also in direct fluid communication, through supply conduit 88, with the inlet 90 of a conventional three-piston control valve 78 which has two control ports 92 and 94 that are connected, via conduits 96 and 98, respectively, with the motor ports 28 and 38, respectively, and has a vent port 100 that isV constantly in communication with atmospheric pressure, as by a return conduit 182 to the sump 86. Preferably, an adiustable pressure release valve 164 is connected into a bypass conduit 106 that is connected between the conduits 82 and 102 to maintain a substantially constant operating pressure for the motor.

The control valve 78 may he set in either of three positions: In the first, the forward pressure chamber 70 ofthe motor is connected to the pressure fluid source and the rear pressure chamber 76 is vented; in the second, both the forward pressure chamber 7i) and the rear pressure chamber 76 are vented; while in lthe third, the rear pressure chamber 76 is pressurized and the forward pressure chamber 70 is vented. It is again pointed out that the intermediate pressure chamber 72 is constantly pressurized. In Figure 4, the valve 78 is illustrated in the second position. Phantom lines illustrate the disposition of the valve when in the first and third positions.

Operation When the piston 54 is in the intermediate position illustrated in Figure 1, and it is desired to actuate a mechanism operatively engaged with the piston rod 36, the control valve 78 is selectively manipulated to the proper position, whereby one `of the end pressure chambers is vented and the other is supplied with pressurized fluid. If, for example, it is desired to extend the piston rod 36, that is to move the piston rod, and hence the piston 54, towards the forward end `of the cylinder, the control valve 78 is manipulated to connect the rear pressure chamber with supply conduit 88, while simultaneously connecting the forward pressure chamber 7@ with the return conduit 102. When these connections are made, pressure chambers 72 and 76 will contain equally pressurized fluid, while pressure chamber 70 will contain Huid at substantially the vent or atmospheric pressure.

It will be seen that the pressure differential between the intermediate pressure `chamber 72 and the forward pressure chamber 70 will be manifested in forwardly directed axial forces acting on the transverse plane of the forward tubularV piston 48. However, as the tubular piston 40 is abutting the plug 14, no motion of the tubular piston 40 will result from these unbalanced forces. The pressure differential between rear pressure chamberl 76 and forward pressure chamber 70 results in unbalanced forwardly directed forces on the planar end -of the piston 2,806,449 n r c e relative to piston 54, as the two members move forwardly as described hereinabove. This forward movement will continue until the pressure in the rear pressure chamber 76 is relieved by manipulation of the control valve 78 `or until the movement is mechanically retarded by the abutment of the forward end `of piston 54 against the forward end plug 14, or by the abutment of the tubular piston 42 against tubular piston 40, the latter of which is held fast as discussed hereinabove. In the preferred embodiment, bes-t illustrated for consideration of this feature in Figure 2, this piston rod extension movement will be mechanically restrained by both of the above-mentioned abutments at substantially the `same instant, although it is 'within the contemplation of this invention that the longitudinal dimension of the piston 54 may be changed with the result that either one or the other of suchy abutments will occur first.

If it is then desired to move the piston rod 36 through the intermediate position to the retracted position illustrated in Figure 3, the control valve 78 is manipulated to supply the forward pressure chamber with pressurized Y fluid while simultaneously connecting the rear pressure chamber 76' to the return conduit 102. The pressure differential between the forward pressure chamber 70 and the rear pressure chamber 76 will result in unbalanced forces upon the planar end of the piston 54 which will move it towards the rear end of the cylinder. Similarly, the pressure differential between the intermediate pressure chamber 72 and the rear pressure chamber 76 will result in unbalanced axial forces upon the tubular piston 42 which will act to move it towards the rear end ofthe cylinder. 62, the tubular piston 42 cannot proceed ahead of the piston 54, rather, it will move with it maintaining a substantially constant relative position therewith. If the tubular piston 42 lags, relatively speaking, behind the piston 54,'the effective operation of the motor is unchanged. As the two pistons, that is the tubular piston 42 and the piston 54, move to the rear, they pass through the intermediate position illustrated in Figure 1 and proceed to the retracted position illustrated in Figure 3. As

the piston 54 moves into the retracted position, its collar 60, in abutting engagement with flange 44, will pull the tubular piston 40 along with it.

As shown in Figure 3, when the motor is 4in the full retracted position, the stub 34 of the piston rod 36 extends within the recess 32 in the rear end does not block the end port38'.

When the piston is located in either the extended or the retracted position and it is desired to transpose it to the intermediate position, the control valve 78 is manipulated to vent both end ports 28 and 38. As the intermediate port 30 is constantly in direct fluid communication with the discharge side of the pump 84, the inter'- mediate pressure chamber 72 will always be supplied with pressurized fluid. This pressure in the intermediate pressure chamber72 results in unbalanced axial forces on the tubular pistons. One of the tubular pistons is held fast in its position abutting its end plug, and the other tubular piston is moved towards the opposite end of the cylinder. The tubular piston which is so moved will pull the piston 54, by engagement of its flange with the collar (60 or 62), in the manner discussed hereinabove, so that the respective elements will arrange themselves in the intermediate position illustrated in Figure 1.

plug 16, but

Due to the abutment of flange 46 and collar Having described only a typical preferred form and i application of my invention, I do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any variations or modiiications that may appear to those skilled in the art and falling within the scope of the following claims.

I claim:

1. A uid pressure motor comprising a cylinder having closed ends; rst and second opposed tubular pistons therein; a third imperforate piston of smaller diameter than said tubular pistons and telescopingly arranged within said tubular pistons and separating the interior of said cylinder into two end pressure chambers and an intermediate pressure chamber; means for connecting each of said chambers with a source of iiuid under pressure; a piston rod connected to said third piston and extending through one of said cylinder ends; a lost motion connection between said third piston and each of said tubular pistons for movement of each of the latter with said third piston when said third piston moves toward the correspondingly opposite end of said cylinder, said lost motion connection being engageable between the third piston and a given tubular piston when the end of the third piston most remote from the given tubular piston moves away from the given tubular piston.

2. The structure defined in claim 1 in which the first and second tubular pistons are dimensioned for substantial abutment against their corresponding cylinder ends when both of the lost motion connections are engaged.

3. The structure deiined in claim 1 including means for supplying the intermediate chamber with pressure uid and means for supplying pressure iluid to and eX- hausting pressure from the end pressure chambers.

4. The structure dened in claim 1 including means for constantly supplying the intermediate chambers with pressure uid and means for alternately supplying pressure uid to one of the end chambers while venting the other, supplying pressure uid to said other end chamber while venting the one, and venting both of said end chambers.

5. A fluid pressure motor comprising a closed cylinder having end ports and an intermediate port; a pair of tandemly aligned tubular pistons within said cylinder; an imperforate piston of smaller diameter than said tubular pistons and telescopingly arranged within each of said tubular pistons and separating the interior of said cylinder into two end pressure chambers and an intermediate pressure chamber; said intermediate port being in constant communication with said intermediate chamber; said intermediate port being constantly connected to a source of fluid pressure; limit means to prevent the complete withdrawal of said imperforate piston from either of said tubular pistons; and sliding sealing means between each of said tubular pistons and said imperforate piston.

6. The structure deiined in claim 5 in which the cylinder has a length substantially equal to the combined length of the tubular pistons and the imperforate piston, when the latter is withdrawn from both of said tubular pistons to the extent deiined by the limit means.

7. The structure defined in claim 6 in which the limit means comprises inwardly extending abutments on the neighboring ends of each of the tubular pistons and spaced outwardly extending abutments on said imperforate piston for engagement with said first-mentioned abutments.

8. The structure dened in claim 7 in which each of the first-mentioned abutments comprises a circumferential iiange having the sealing means disposed in the periphery thereof.

9. The structure defined in claim 8 and further including a three-position Valve having the end ports connected thereto for selectively connecting one end port with the pressure source while venting the other end port, connecting the other end port to said pressure source While venting the one end port, and venting both end ports simultaneously.

10. A iluid pressure motor comprising a closed cylinder; a pair of tandemly aligned tubular pistons, said tubular pistons being slidably sealingly disposed within said cylinder; a third piston having one end slidably sealingly disposed within one of said tubular pistons and having the other end slidably sealingly disposed within the other of said tubular pistons, limit means for preventing a complete withdrawal of said third piston from either of said tubular pistons and forming lost motion connections therebetween; said limit means comprising outwardly eX- tending formations on the exterior periphery of the third piston having an exterior diameter less than lthe interior diameter of said tubular piston, and inwardly extending projections formed on the interior periphery of said tubular pistons, and having an interior diameter greater than the diameter of said third piston; said cylinder having end ports at each end thereof to selectively conduct pressure iiuid to axially urge all of said pistons towards the opposite end of said cylinder; said cylinder having an intermediate port for conducting pressure fluid to axially displace at least one of said tubular pistons toward one of said ends; and a piston rod connected to said third piston and extending without said closed cylinder.

l1. The structure defined in claim 10 in which the intermediate port is constantly connected to a source of iluid pressure; and including -a three-position valve having the end ports connected thereto for selectively connecting one end port with the pressure source while venting the other end port, connecting the other end port to said pressure source while venting the one end port, and venting both end ports simultaneously.

Bromley 'Aug. 16, 1904 Stevens Oct. 3, 1950 

